ABSTRACT
Objective: To observe the development of dentinal microcracks after root canal preparation with there kinds of reciprocating nickel-titaninm instruments using an in situ cadaver model by means of micro-computed tomography (Micro CT), and to provide the reference for their clinical application. Methods: A total of 15 mandible bone specimens having at least the anterior teeth (n=60) with single root were selected and there was no dentina microcrack, then they were randomly divided into 4 groups (n=15) according to the preparation protocol: Wave One, Reciproc, One File and ProTaper Universal groups, and ProTaper Universal was used as control group. The root canals were prepared up to 25 # instruments in Wave One, Reciproc and One File groups and F2 instruments in ProTaper Universal groups. After the preparation procedures, the specimens were scanned by Micro CT again, and the number of dentinal microcracks were investigated and analyzed statistically. Results: Compared with ProTaper Universal group, the incidence rates in Wave One, Reciproc and One File groups were significantly reduced (P0. 05). Conclusion: Root canal preparation can cause the dentinal microcracks, so it is important to choose the types of instruments. Root canals prepared with Reciproc, Wave One and One File produce less dentinal microcracks, which can decrease the risk of vertical root fracture.
ABSTRACT
Objective@# To compare the differences in the stress distribution in simulated first molars prepared with three rotary nickel-titanium instruments. @*Methods @#Four simulated first molars were prepared without instruments and with Reciproc, WaveOne and Protaper. Before and after preparation, each simulated molar was scanned by Micro-CT. The data were imported to Mimics 16.0 software to establish three-dimensional models. Finite element analysis was processed with Abaqus 6.14 software under conditions of longitudinal and lateral load. @*Results@# Under vertical load conditions, the maximum von Mises stress of the enamel increased by 1.36%, 21.48% and 20.99% in the Reciproc, WaveOne and Protaper groups, respectively, after preparation, while the maximum von Mises stress of the cementum increased by 55.98%, 41.18% and 33.04%, respectively, and the maximum von Mises stress of the alveolar bone increased by 45.55%, 40.37% and 24.09%, respectively. Under 45° lateral load conditions, the maximum von Mises stress of the enamel increased by 1.79%, -4.58% and 3.82% in the Reciproc, WaveOne and Protaper groups, respectively, after preparation, while the maximum von Mises stress of cementum increased by 16.33%, 7.58% and 4.32%, respectively, and the maximum von Mises stress of the alveolar bone increased by 46.82%, 36.40% and 8.29%, respectively. Under the same conditions, the von Mises stresses of the cementum and alveolar bones of the simulated molars were higher after preparation than before preparation, especially under lateral load conditions. The stress was focused on the border between the crown and the root. The von Mises stress of the cementum and alveolar bones increased much more in the Reciproc group than in the other two groups under both conditions.@*Conclusion@#The von Mises stress of simulated molars was greater after preparation than before preparation. The von Mises stress of the cementum and alveolar bones increased much more in the Reciproc group than in the other two groups.
ABSTRACT
Objective:To observe the development of dentinal microcracks after root canal preparation with there kinds of reciprocating nickel-titaninm instruments using an in situ cadaver model by means of micro-computed tomography (Micro CT),and to provide the reference for their clinical application.Methods:A total of 15 mandible bone specimens having at least the anterior teeth (n=60) with single root were selected and there was no dentina microcrack,then they were randomly divided into 4 groups (n=15) according to the preparation protocol:Wave One,Reciproc,One File and ProTaper Universal groups,and ProTaper Universal was used as control group.The root canals were prepared up to 25 # instruments in Wave One,Reciproc and One File groups and F2 instruments in ProTaper Universal groups.After the preparation procedures,the specimens were scanned by Micro CT again,and the number of dentinal microcracks were investigated and analyzed statistically.Results:Compared with ProTaper Universal group,the incidence rates in Wave One,Reciproc and One File groups were significantly reduced (P＜0.05).There were no statistical differences in the incidence rates of dentinal microcracks between Wave One,Reciproc and One File groups (P＞0.05).Conclusion:Root canal preparation can cause the dentinal microcracks,so it is important to choose the types of instruments.Root canals prepared with Reciproc,Wave One and One File produce less dentinal microcracks,which can decrease the risk of vertical root fracture.
ABSTRACT
Objective To compare the centering ability of three rotary nickel-titanium instruments Reciproc,Protaper and WaveOne in resin-simulated curved root canals.Methods A total of 30 resin-simulated curved canals(curvature=30°)were di-vided into 3 groups(n=10 each)using the random number table.They were prepared with Reciproc(group R),Protaper(group P)and WaveOne(group W)respectively.Pre-and post-operative images were obtained by a digital camera at the fixed position, and superimposed through Photoshop.The center displacement between pre- and post-operative images were measured at 10 points beginning at 1 mm from the end point of the canal with the software Digimizer at a ratio of 1 to 1.The data were analyzed through one-way ANOVA and Student-Newman-Kuels at a significance level ofα=0.05.Results The central point was shifted laterally to the curve at 1,2,and 3 mm from the end point of the canal,while it shifted medially to the curve at 6,7,and 8 mm.The centering ability was better in groups R and W than in group P with significant differences noted(P <0.05).No sig-nificant difference was found in the centering ability between group R and group W.Also there were no significant differences in the centering ability at 4,5,9 and 10 mm among the three groups(P >0.05).Conclusion Reciproc and WaveOne have similar centering ability.They preform better in terms of centering location than Protaper,especially at the apex and the most curved part of the canal.